Draw a diagram for every situation in mechanics, it always helps.
Resolving perpendicular:
R=400gcos15
Resolving parallel:
T + 0.2R = 400gsin15
T = 400gsin15 - 0.2[400gcos15]
T = 400g[sin15-0.2cos15]
T = 257.3N
F=ma
400gsin15-0.2R = 400a
400gsin15 - 0.2[400gcos15] = 400a
a= 0.643ms^-2
s=50, a=0.643, t=0, t=?
s=ut+0.5at^2
50=(0.643/2)t^2
t=12.5sec(3sf)